<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <title>1.apply</title>
  </head>
  <body>
    <script type="text/javascript" >

      function test (){
        console.log(this)
      }

      test()
      let vm = {a:1}
      test.apply(vm)
    </script>
  </body>
</html>